1 Department of Chemical and Materials Engineering, Concordia University, Montreal, Quebec, Canada.
2 Department of Mechanical, Industrial & Aerospace Engineering, Concordia University, Montreal, Quebec, Canada.
3 Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, Canada.
4 Canadian Light Source Inc., University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
5 Department of Chemistry, University of Western Ontario, London, Ontario, Canada.
6 Surface Science Western, University of Western Ontario, 999 Collip Circle, London, Ontario, Canada.
7 Department of Physics and Astronomy, University of Western Ontario, 1151 Richmond St, London, Ontario, Canada.
8 Department of Chemical and Materials Engineering, Concordia University, Montreal, Quebec, Canada. xia.li@concordia.ca.

Sustainable and cost-effective organic electrode materials are promising for next-generation lithium-ion batteries but are hindered by severe shuttle effects. While all-solid-state batteries offer a potential solution, chemical and mechanical incompatibility between organic electrode materials and inorganic solid electrolytes limit areal capacity and cycling stability, falling short of practical requirements. Here, we report a bifunctional indigo natural dye that serves as both an active material and a solid molecular catalyst in sulfide-based all-solid-state batteries, addressing these compatibility challenges. Contrary to the prevailing view that chemical reactions between organic electrode materials and sulfide solid electrolytes are detrimental, our study reveals that controlled reactions between indigo and Li₆PS₅Cl solid electrolyte catalyze their synergistic redox process after optimizing electrode microstructures. This strategy enables a high reversible capacity of 583 mAh g^-1 (Li₆PS₅Cl contribution: 379 mAh g^-1) at 0.1 C, a high areal capacity of 3.84 mAh cm^-2, and good cycling stability at an operation temperature of 25 °C. These findings highlight the potential of bifunctional organic electrode materials in sulfide-based all-solid-state batteries to overcome the key challenges of organic electrode materials in practical applications.